Look to Gawker for some of the best headlines on the web. A personal favourite: In Sweden They Market Pet Insurance with Synchronized Skydiving Cats Set to R. Kelly

A point was made up above about looking at women's magazines on the newsstand. It's a great point. Standing in a newsagent or supermarket and looking at the magazines in your niche to see what sort of stuff they're covering and how they're 'selling' the mag with their coverlines is something I do regularly.

Even better, you can do it from the comfort of your desk chair by looking at Zinio or the Apple newsstand. It's probably best to look at Apple's UK newsstand as the American business model for print magazines is based more on subscriptions, so their covers don't have to work as hard to sell the content via lots of coverlines. In the UK there's more emphasis in sales from newsstand, so you'll find a lot more coverlines for inspiration.